In medicine, it is used in bone cement and to replace eye lenses. It is extensively used to make signs, including lettering and logos. It serves as a sturdy substitute for glass for items such as aquariums, buttons, motorcycle helmet visors, aircraft windows, viewing ports of submersibles, and lenses of exterior lights of automobiles. PMMA is also known by trade names such as Lucite, Perspex and Plexiglas. Today’s acrylics industry can be divided into two distinct multibillion-dollar markets: on one hand the polyacrylic acids (PAA) and its ester derivatives (PAc) market, on the other hand, the poly(methyl methacrylate) (PMMA) market. These are linear or slightly branched long chain molecules capable of repeatedly softening on heating and hardening on cooling. Before these techniques were employed, plastic automobile parts would often crack when exposed to cold temperatures. Modification of the polymer through copolymerization or through the addition of non-reactive side chains to monomers before polymerization can also lower it. Amorphous and semi-amorphous plastics are less resistant to chemical attack and environmental stress cracking because they lack a crystalline structure.īrittleness can be decreased with the addition of plasticizers, which increases the mobility of amorphous chain segments to effectively lower the glass transition temperature. Amorphous and semi-amorphous plastics are used when high optical clarity is necessary, as light is scattered strongly by crystallites larger than its wavelength. Some thermoplastics do not fully crystallize below the glass transition temperature, retaining some or all of their amorphous characteristics. Stress-strain graph of a thermoplastic materialĪbove its glass transition temperature and below its melting point, the physical properties of a thermoplastic change drastically without an associated phase change. Thermosets do not melt when heated, but typically decompose and do not reform upon cooling. Thermoplastics differ from thermosetting polymers (or "thermosets"), which form irreversible chemical bonds during the curing process. In this state, thermoplastics may be reshaped, and are typically used to produce parts by various polymer processing techniques such as injection molding, compression molding, calendering, and extrusion. The polymer chains associate by intermolecular forces, which weaken rapidly with increased temperature, yielding a viscous liquid. Most thermoplastics have a high molecular weight. JSTOR ( March 2021) ( Learn how and when to remove this template message)Ī thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. ![]() ![]() Unsourced material may be challenged and removed. Please help improve this article by adding citations to reliable sources. ![]() This article needs additional citations for verification.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |